Lavrov told the Russia Today (RT) television channel that recent signs that parts of Syria's chemical arsenal were being moved – a development that alarmed Western governments – was an effort by the government to make the weapons more secure.
This correlated with information the US has, he said.
Citing European and US officials, media reports in early December said Syria's chemical weapons had been moved and could be primed for use in response to any dramatic gains by rebels fighting to topple Assad in a conflict that has killed more than 40,000 people since March 2011.
Syrian rebels (Photo: Reuters)
The United States warned it would take action against such an escalation, though Syria said it would never use chemical weapons against its own people.
"I don't believe Syria would use chemical weapons," Lavrov told RT. "It would be political suicide for the government if it does."
Russia has angered the West and some Arab states by vetoing three UN Security Council resolutions meant to put pressure on Assad.
In his RT interview, Lavrov defended Russia's position, stressing Moscow's opposition to military intervention.
It is unclear whether Russia intends to evacuate its citizens from Syria. Russia's Interfax cited a naval source as saying last week that Russia had sent warships from the Baltic Sea to the Mediterranean in case it had to do so.
Russian fuel shipment arrives in Syria
Also on Monday, two cargoes of Russian diesel have reached the war-ravaged country, providing the first significant volumes in months of the fuel it desperately needs to power industry and the military, generate electricity and heat homes.
Both shipments were transported from Russia on Italian tankers to a port controlled by Assad's forces, but it was unclear who was behind the shipments. Nor was there any evidence they violated sanctions against Syria.
"(Our vessels) loaded two cargoes of gasoil in Russia at the beginning of December for delivery to the East Mediterranean. The charterer then asked us to deliver the volumes to Banias," said Paolo Cagnoni, who heads Mediterranea di Navigazione S.p.A., the family-run Italian tanker firm.
He declined to disclose the names of the vessel charterers and the recipient of the deliveries, which amount to around 42,000 tonnes of gasoil worth close to $40 million at current market prices.
Shortages of diesel and other fuels in Syria have grown severe since the European Union introduced tighter sanctions in March.
Trading firms that previously did business with Syria have dropped out of the market for fear of falling foul of the rules or becoming associated with Assad's bloody crackdown on civil unrest.
Reuters and AFP contributed to this report
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